GNU bug report logs - #6740
Spurious byte compiler warnings

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Message #14 received at 6740 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Dan Nicolaescu <dann <at> gnu.org>
Cc: Alan Mackenzie <acm <at> muc.de>, 6740 <at> debbugs.gnu.org
Subject: Re: bug#6740: Spurious byte compiler warnings
Date: Tue, 27 Jul 2010 23:40:50 +0200

>> Warning: value returned from (featurep (quote cc-fix)) is unused
>> Warning: value returned from (featurep (quote cc-fix)) is unused
>> 
>> It is obvious that that value is indeed used.  This is a bug.

> The byte compiler knows that (featurep 'xemacs) is false, so 
>  (and (not (featurep 'cc-fix)) ... )
> will be false, so the featurep result is indeed unused.

> If you use (and (featurep 'xemacs) (not (featurep 'cc-fix) ...
> the warning will go away.

It's one of those cases where the warning is the result of a check done
"too late" (i.e. after some optimization), which means the check is not
performed on the code the user sees, but on some massaged version of it.
It's difficult to avoid them, short of removing all "code
improvement" warnings.


        Stefan

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